AtCoder Beginner Contest 169

题目传送门

视频题解

BC是一些常见的技巧，D题很水，E比较有意思，考虑成为中位数的充要条件即可，主要是注意到某些不与相交的区间个数。F的话是一个不是很难的dp，把计算过程分散到dp过程即可。具体的话可以看看视频题解。

---

以下是代码：

A - Multiplication 1

/*
 * Author:  heyuhhh
 * Created Time:  2020/5/31 20:00:31
 */
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#include <functional>
#include <numeric>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
  #define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
  void err() { std::cout << std::endl; }
  template<typename T, typename...Args>
  void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
  template <template<typename...> class T, typename t, typename... A> 
  void err(const T <t> &arg, const A&... args) {
  for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
  #define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 1e5 + 5;

void run() {
    int a, b; cin >> a >> b;
    cout << a * b << '
';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cout << fixed << setprecision(20);
    run();
    return 0;
}

B - Multiplication 2

/*
 * Author:  heyuhhh
 * Created Time:  2020/5/31 20:01:06
 */
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#include <functional>
#include <numeric>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
  #define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
  void err() { std::cout << std::endl; }
  template<typename T, typename...Args>
  void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
  template <template<typename...> class T, typename t, typename... A> 
  void err(const T <t> &arg, const A&... args) {
  for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
  #define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 1e5 + 5;
const ll MAX = 1e18;

void run() {
    int n; cin >> n;
    vector <ll> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    for (int i = 0; i < n; i++) if (a[i] == 0) {
        cout << 0 << '
';
        return;
    }
    ll ans = 1;
    for (int i = 0; i < n; i++) {
        if (a[i] > MAX / ans) {
            cout << -1 << '
';
            return;
        }
        ans *= a[i];
    }
    cout << ans << '
';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cout << fixed << setprecision(20);
    run();
    return 0;
}

C - Multiplication 3

/*
 * Author:  heyuhhh
 * Created Time:  2020/5/31 20:11:10
 */
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#include <functional>
#include <numeric>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
  #define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
  void err() { std::cout << std::endl; }
  template<typename T, typename...Args>
  void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
  template <template<typename...> class T, typename t, typename... A> 
  void err(const T <t> &arg, const A&... args) {
  for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
  #define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 1e5 + 5;
const double eps = 1e-7;

void run() {
    ll A;
    double B;
    cin >> A >> B;
    ll C = ll(B * 100 + 0.5);
    ll ans = A * C;
    cout << ll(ans / 100) << '
';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cout << fixed << setprecision(20);
    run();
    return 0;
}

D - Div Game

/*
 * Author:  heyuhhh
 * Created Time:  2020/5/31 20:16:37
 */
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#include <functional>
#include <numeric>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
  #define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
  void err() { std::cout << std::endl; }
  template<typename T, typename...Args>
  void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
  template <template<typename...> class T, typename t, typename... A> 
  void err(const T <t> &arg, const A&... args) {
  for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
  #define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 1e5 + 5;

void run() {
    ll n; cin >> n;
    int ans = 0;
    for (int i = 2; 1ll * i * i <= n; i++) {
        if (n % i == 0) {
            int cnt = 0;
            int tot = 1;
            while (n % i == 0) {
                n /= i;
                ++cnt;  
                if (cnt == tot) {
                    cnt = 0;
                    ++ans;
                    ++tot;  
                } 
            }
        }   
    }
    if (n > 1) ++ans;
    cout << ans << '
';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cout << fixed << setprecision(20);
    run();
    return 0;
}

E - Count Median

/*
 * Author:  heyuhhh
 * Created Time:  2020/5/31 20:46:05
 */
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#include <functional>
#include <numeric>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
  #define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
  void err() { std::cout << std::endl; }
  template<typename T, typename...Args>
  void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
  template <template<typename...> class T, typename t, typename... A> 
  void err(const T <t> &arg, const A&... args) {
  for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
  #define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 2e5 + 5;

struct seg {
    int l, r;   
}a[N];

int n;

int findL(int k) {
    return a[k + 1].r;
}

int findR(int k) {
    return a[k + 1].l;
}

seg find(int k) {
    sort(a + 1, a + n + 1, [&](seg A, seg B) {
        return A.r < B.r;
    });
    int r = findL(k - 1);
    sort(a + 1, a + n + 1, [&](seg A, seg B) {
        return A.l > B.l;
    });   
    int l = findR(n - k);
    return seg{l, r};
}

void run() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
        int l, r; cin >> l >> r;
        a[i] = seg{l, r};
    }
    if (n & 1) {
        seg res = find(n / 2 + 1);
        int ans = max(0, res.r - res.l + 1); 
        cout << ans << '
';
    } else {
        seg res1 = find(n / 2), res2 = find(n / 2 + 1);
        int Min = res1.l + res2.l, Max = res1.r + res2.r;
        int ans = max(0, Max - Min + 1);
        cout << ans << '
';
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cout << fixed << setprecision(20);
    run();
    return 0;
}

F - Knapsack for All Subsets

/*
 * Author:  heyuhhh
 * Created Time:  2020/5/31 21:11:22
 */
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#include <iomanip>
#include <assert.h>
#include <functional>
#include <numeric>
#define MP make_pair
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define INF 0x3f3f3f3f
#define Local
#ifdef Local
  #define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
  void err() { std::cout << std::endl; }
  template<typename T, typename...Args>
  void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
  template <template<typename...> class T, typename t, typename... A> 
  void err(const T <t> &arg, const A&... args) {
  for (auto &v : arg) std::cout << v << ' '; err(args...); }
#else
  #define dbg(...)
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
//head
const int N = 3000 + 5, MOD = 998244353;
int qpow(ll a, ll b) {
    ll res = 1;
    while (b) {
        if (b & 1) res = res * a % MOD;
        a = a * a % MOD;
        b >>= 1;
    }   
    return res;
}

int n, s;
int a[N];
int dp[N][N];

void add(int& x, int y) {
    x += y;
    if (x >= MOD) x -= MOD;   
}

void run() {
    cin >> n >> s;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    dp[0][0] = qpow(2, n);
    int inv2 = (MOD + 1) / 2;
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j <= s; j++) {
            if (j >= a[i]) {
                dp[i][j] = 1ll * dp[i - 1][j - a[i]] * inv2 % MOD;
            }
            dp[i][j] = (dp[i][j] + dp[i - 1][j]) % MOD;
        }
    }
    cout << dp[n][s] << '
';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cout << fixed << setprecision(20);
    run();
    return 0;
}